Agree with your suggestion to deploy packet sniffing software to get to the root of this issue. Although I hardly think this is an application bug but more of a network issue.

This is a network issue and probably not one related to oracle database.

Also if possible the next time before someone logs in to the database you can probably try tnsping for the database from a client to see if the connection is being made to the database or not, I'm quiet certain that the connection request is not reaching the database.

Once this is confirmed you can connect with your network team to narrow down on the real issue.

Agree with your suggestion to deploy packet sniffing software to get to the root of this issue. Although I hardly think this is an application bug but more of a network issue.

This is a network issue and probably not one related to oracle database.

Also if possible the next time before someone logs in to the database you can probably try tnsping for the database from a client to see if the connection is being made to the database or not, I'm quiet certain that the connection request is not reaching the database.

Once this is confirmed you can connect with your network team to narrow down on the real issue.

Raju, what full version of Oracle is the target datbase? What kind of applciation? Running locally or remote using what version of the Oracle client? What full version of the OS supports the database, the applciation?

We have encountered numerous ORA-03114 errors over the years which would occur causing the existing connection to be broken, but almost all of these errors were due to version specific bugs and a couple of these bugs were also platform specific.

Do you have DCD (dead connection detection) in use? There is an Oracle support note 1550470.1 about DCD and this issue. There are also current notes for EBS auto-invoicing, datapump, rman, and some other products hitting this error but I did not see any note about just connecting.

Since you should know what kind of front-end application is in use and the code base it is written in you should be able to perform a better problem search on support.

Instead of spending time here, as somebody suggested above , start the client level 16 trace on your application server and upload those to support or here. Somebody should be able to read and diagnose from those traces. It should be easy because its not intermittent and you have a pattern when that error occurs.You do not have to wait. Just start the trace right before you start the app and close it right after you get the error in order to avoid the huge log.

Also, Do you start the application everyday? Keep an eye on the system resource when you try to connect to oracle for first time everyday.

Are you sure it is not something like the user starting to work before dns has properly served the location of the server? I often have that issue with my home ISP and websites, no Oracle involved. A couple of reload page and all is fine. Stupid ISP.